fd.c

   1 /*
   2  * Copyright (C) 2006-2009 Andre Noll <maan@systemlinux.org>
   3  *
   4  * Licensed under the GPL v2. For licencing details see COPYING.
   5  */
   6
   7 /** \file fd.c Helper functions for file descriptor handling. */
   8
   9 #include <regex.h>
  10 #include <sys/types.h>
  11 #include <dirent.h>
  12 #include <sys/mman.h>
  13 #include <fcntl.h>
  14 #include <sys/select.h>
  15
  16 #include "para.h"
  17 #include "error.h"
  18 #include "string.h"
  19
  20 /**
  21  * Write a buffer to a file descriptor, re-write on short writes.
  22  *
  23  * \param fd The file descriptor.
  24  * \param buf The buffer to be sent.
  25  * \param len The length of \a buf.
  26  *
  27  * \return Standard. In any case, the number of bytes that have been written is
  28  * stored in \a len.
  29  */
  30 int write_all(int fd, const char *buf, size_t *len)
  31 {
  32         size_t total = *len;
  33
  34         assert(total);
  35         *len = 0;
  36         while (*len < total) {
  37                 int ret = write(fd, buf + *len, total - *len);
  38                 if (ret == -1)
  39                         return -ERRNO_TO_PARA_ERROR(errno);
  40                 *len += ret;
  41         }
  42         return 1;
  43 }
  44
  45 /**
  46  * Write a buffer to a non-blocking file descriptor.
  47  *
  48  * \param fd The file descriptor.
  49  * \param buf the buffer to write.
  50  * \param len the number of bytes of \a buf.
  51  * \param max_bytes_per_write Do not write more than that many bytes at once.
  52  *
  53  * If \a max_bytes_per_write is non-zero, do not send more than that many bytes
  54  * per write().
  55  *
  56  * EAGAIN is not considered an error condition.  For example CCID3 has a
  57  * sending wait queue which fills up and is emptied asynchronously. The EAGAIN
  58  * case means that there is currently no space in the wait queue, but this can
  59  * change at any moment.
  60  *
  61  * \return Negative on errors, number of bytes written else.
  62  */
  63 int write_nonblock(int fd, const char *buf, size_t len,
  64                 size_t max_bytes_per_write)
  65 {
  66         size_t written = 0;
  67         int ret = 0;
  68
  69         while (written < len) {
  70                 size_t num = len - written;
  71
  72                 if (max_bytes_per_write && max_bytes_per_write < num)
  73                         num = max_bytes_per_write;
  74                 ret = write(fd, buf + written, num);
  75                 if (ret < 0 && errno == EAGAIN)
  76                         return written;
  77                 if (ret < 0)
  78                         return -ERRNO_TO_PARA_ERROR(errno);
  79                 written += ret;
  80         }
  81         return written;
  82 }
  83
  84 /**
  85  * Check whether a file exists.
  86  *
  87  * \param fn The file name.
  88  *
  89  * \return Non-zero iff file exists.
  90  */
  91 int file_exists(const char *fn)
  92 {
  93         struct stat statbuf;
  94
  95         return !stat(fn, &statbuf);
  96 }
  97
  98 /**
  99  * Paraslash's wrapper for select(2).
 100  *
 101  * It calls select(2) (with no exceptfds) and starts over if select() was
 102  * interrupted by a signal.
 103  *
 104  * \param n The highest-numbered descriptor in any of the two sets, plus 1.
 105  * \param readfds fds that should be checked for readability.
 106  * \param writefds fds that should be checked for writablility.
 107  * \param timeout_tv upper bound on the amount of time elapsed before select()
 108  * returns.
 109  *
 110  * \return The return value of the underlying select() call on success, the
 111  * negative system error code on errors.
 112  *
 113  * All arguments are passed verbatim to select(2).
 114  * \sa select(2) select_tut(2).
 115  */
 116 int para_select(int n, fd_set *readfds, fd_set *writefds,
 117                 struct timeval *timeout_tv)
 118 {
 119         int ret;
 120         do
 121                 ret = select(n, readfds, writefds, NULL, timeout_tv);
 122         while (ret < 0 && errno == EINTR);
 123         if (ret < 0)
 124                 return -ERRNO_TO_PARA_ERROR(errno);
 125         return ret;
 126 }
 127
 128 /**
 129  * Set a file descriptor to blocking mode.
 130  *
 131  * \param fd The file descriptor.
 132  *
 133  * \return Standard.
 134  */
 135 __must_check int mark_fd_blocking(int fd)
 136 {
 137         int flags = fcntl(fd, F_GETFL);
 138         if (flags < 0)
 139                 return -ERRNO_TO_PARA_ERROR(errno);
 140         flags = fcntl(fd, F_SETFL, ((long)flags) & ~O_NONBLOCK);
 141         if (flags < 0)
 142                 return -ERRNO_TO_PARA_ERROR(errno);
 143         return 1;
 144 }
 145
 146 /**
 147  * Set a file descriptor to non-blocking mode.
 148  *
 149  * \param fd The file descriptor.
 150  *
 151  * \return Standard.
 152  */
 153 __must_check int mark_fd_nonblocking(int fd)
 154 {
 155         int flags = fcntl(fd, F_GETFL);
 156         if (flags < 0)
 157                 return -ERRNO_TO_PARA_ERROR(errno);
 158         flags = fcntl(fd, F_SETFL, ((long)flags) | O_NONBLOCK);
 159         if (flags < 0)
 160                 return -ERRNO_TO_PARA_ERROR(errno);
 161         return 1;
 162 }
 163
 164 /**
 165  * Set a file descriptor in a fd_set.
 166  *
 167  * \param fd The file descriptor to be set.
 168  * \param fds The file descriptor set.
 169  * \param max_fileno Highest-numbered file descriptor.
 170  *
 171  * This wrapper for FD_SET() passes its first two arguments to \p FD_SET. Upon
 172  * return, \a max_fileno contains the maximum of the old_value and \a fd.
 173  *
 174  * \sa para_select.
 175 */
 176 void para_fd_set(int fd, fd_set *fds, int *max_fileno)
 177 {
 178         assert(fd >= 0 && fd < FD_SETSIZE);
 179 #if 0
 180         {
 181                 int flags = fcntl(fd, F_GETFL);
 182                 if (!(flags & O_NONBLOCK)) {
 183                         PARA_EMERG_LOG("fd %d is a blocking file descriptor\n", fd);
 184                         exit(EXIT_FAILURE);
 185                 }
 186         }
 187 #endif
 188         FD_SET(fd, fds);
 189         *max_fileno = PARA_MAX(*max_fileno, fd);
 190 }
 191
 192 /**
 193  * Paraslash's wrapper for fgets(3).
 194  *
 195  * \param line Pointer to the buffer to store the line.
 196  * \param size The size of the buffer given by \a line.
 197  * \param f The stream to read from.
 198  *
 199  * \return Unlike the standard fgets() function, an integer value
 200  * is returned. On success, this function returns 1. On errors, -E_FGETS
 201  * is returned. A zero return value indicates an end of file condition.
 202  */
 203 __must_check int para_fgets(char *line, int size, FILE *f)
 204 {
 205 again:
 206         if (fgets(line, size, f))
 207                 return 1;
 208         if (feof(f))
 209                 return 0;
 210         if (!ferror(f))
 211                 return -E_FGETS;
 212         if (errno != EINTR) {
 213                 PARA_ERROR_LOG("%s\n", strerror(errno));
 214                 return -E_FGETS;
 215         }
 216         clearerr(f);
 217         goto again;
 218 }
 219
 220 /**
 221  * Paraslash's wrapper for mmap.
 222  *
 223  * \param length Number of bytes to mmap.
 224  * \param prot Either PROT_NONE or the bitwise OR of one or more of
 225  * PROT_EXEC PROT_READ PROT_WRITE.
 226  * \param flags Exactly one of MAP_SHARED and MAP_PRIVATE.
 227  * \param fd The file to mmap from.
 228  * \param offset Mmap start.
 229  * \param map Result pointer.
 230  *
 231  * \return Standard.
 232  *
 233  * \sa mmap(2).
 234  */
 235 int para_mmap(size_t length, int prot, int flags, int fd, off_t offset,
 236                 void *map)
 237 {
 238         void **m = map;
 239
 240         errno = EINVAL;
 241         if (!length)
 242                 goto err;
 243         *m = mmap(NULL, length, prot, flags, fd, offset);
 244         if (*m != MAP_FAILED)
 245                 return 1;
 246 err:
 247         *m = NULL;
 248         return -ERRNO_TO_PARA_ERROR(errno);
 249 }
 250
 251 /**
 252  * Wrapper for the open(2) system call.
 253  *
 254  * \param path The filename.
 255  * \param flags The usual open(2) flags.
 256  * \param mode Specifies the permissions to use.
 257  *
 258  * The mode parameter must be specified when O_CREAT is in the flags, and is
 259  * ignored otherwise.
 260  *
 261  * \return The file descriptor on success, negative on errors.
 262  *
 263  * \sa open(2).
 264  */
 265 int para_open(const char *path, int flags, mode_t mode)
 266 {
 267         int ret = open(path, flags, mode);
 268
 269         if (ret >= 0)
 270                 return ret;
 271         return -ERRNO_TO_PARA_ERROR(errno);
 272 }
 273
 274 /**
 275  * Wrapper for chdir(2).
 276  *
 277  * \param path The specified directory.
 278  *
 279  * \return Standard.
 280  */
 281 int para_chdir(const char *path)
 282 {
 283         int ret = chdir(path);
 284
 285         if (ret >= 0)
 286                 return 1;
 287         return -ERRNO_TO_PARA_ERROR(errno);
 288 }
 289
 290 /**
 291  * Save the cwd and open a given directory.
 292  *
 293  * \param dirname Path to the directory to open.
 294  * \param dir Result pointer.
 295  * \param cwd File descriptor of the current working directory.
 296  *
 297  * \return Standard.
 298  *
 299  * Opening the current directory (".") and calling fchdir() to return is
 300  * usually faster and more reliable than saving cwd in some buffer and calling
 301  * chdir() afterwards.
 302  *
 303  * If \a cwd is not \p NULL "." is opened and the resulting file descriptor is
 304  * stored in \a cwd. If the function returns success, and \a cwd is not \p
 305  * NULL, the caller must close this file descriptor (probably after calling
 306  * fchdir(*cwd)).
 307  *
 308  * On errors, the function undos everything, so the caller needs neither close
 309  * any files, nor change back to the original working directory.
 310  *
 311  * \sa getcwd(3).
 312  *
 313  */
 314 int para_opendir(const char *dirname, DIR **dir, int *cwd)
 315 {
 316         int ret;
 317
 318         if (cwd) {
 319                 ret = para_open(".", O_RDONLY, 0);
 320                 if (ret < 0)
 321                         return ret;
 322                 *cwd = ret;
 323         }
 324         ret = para_chdir(dirname);
 325         if (ret < 0)
 326                 goto close_cwd;
 327         *dir = opendir(".");
 328         if (*dir)
 329                 return 1;
 330         ret = -ERRNO_TO_PARA_ERROR(errno);
 331         /* Ignore return value of fchdir() and close(). We're busted anyway. */
 332         if (cwd) {
 333                 int __a_unused ret2 = fchdir(*cwd); /* STFU, gcc */
 334         }
 335 close_cwd:
 336         if (cwd)
 337                 close(*cwd);
 338         return ret;
 339 }
 340
 341 /**
 342  * A wrapper for fchdir().
 343  *
 344  * \param fd An open file descriptor.
 345  *
 346  * \return Standard.
 347  */
 348 int para_fchdir(int fd)
 349 {
 350         if (fchdir(fd) < 0)
 351                 return -ERRNO_TO_PARA_ERROR(errno);
 352         return 1;
 353 }
 354
 355 /**
 356  * A wrapper for mkdir(2).
 357  *
 358  * \param path Name of the directory to create.
 359  * \param mode The permissions to use.
 360  *
 361  * \return Standard.
 362  */
 363 int para_mkdir(const char *path, mode_t mode)
 364 {
 365         if (!mkdir(path, mode))
 366                 return 1;
 367         return -ERRNO_TO_PARA_ERROR(errno);
 368 }
 369
 370 /**
 371  * Open a file and map it into memory.
 372  *
 373  * \param path Name of the regular file to map.
 374  * \param open_mode Either \p O_RDONLY or \p O_RDWR.
 375  * \param map On success, the mapping is returned here.
 376  * \param size size of the mapping.
 377  * \param fd_ptr The file descriptor of the mapping.
 378  *
 379  * If \a fd_ptr is \p NULL, the file descriptor resulting from the underlying
 380  * open call is closed after mmap().  Otherwise the file is kept open and the
 381  * file descriptor is returned in \a fd_ptr.
 382  *
 383  * \return Standard.
 384  *
 385  * \sa para_open(), mmap(2).
 386  */
 387 int mmap_full_file(const char *path, int open_mode, void **map,
 388                 size_t *size, int *fd_ptr)
 389 {
 390         int fd, ret, mmap_prot, mmap_flags;
 391         struct stat file_status;
 392
 393         if (open_mode == O_RDONLY) {
 394                 mmap_prot = PROT_READ;
 395                 mmap_flags = MAP_PRIVATE;
 396         } else {
 397                 mmap_prot = PROT_READ | PROT_WRITE;
 398                 mmap_flags = MAP_SHARED;
 399         }
 400         ret = para_open(path, open_mode, 0);
 401         if (ret < 0)
 402                 return ret;
 403         fd = ret;
 404         if (fstat(fd, &file_status) < 0) {
 405                 ret = -ERRNO_TO_PARA_ERROR(errno);
 406                 goto out;
 407         }
 408         *size = file_status.st_size;
 409         ret = para_mmap(*size, mmap_prot, mmap_flags, fd, 0, map);
 410 out:
 411         if (ret < 0 || !fd_ptr)
 412                 close(fd);
 413         else
 414                 *fd_ptr = fd;
 415         return ret;
 416 }
 417
 418 /**
 419  * A wrapper for munmap(2).
 420  *
 421  * \param start The start address of the memory mapping.
 422  * \param length The size of the mapping.
 423  *
 424  * \return Standard.
 425  *
 426  * \sa munmap(2), mmap_full_file().
 427  */
 428 int para_munmap(void *start, size_t length)
 429 {
 430         int err;
 431         if (munmap(start, length) >= 0)
 432                 return 1;
 433         err = errno;
 434         PARA_ERROR_LOG("munmap (%p/%zu) failed: %s\n", start, length,
 435                 strerror(err));
 436         return -ERRNO_TO_PARA_ERROR(err);
 437 }
 438
 439 /**
 440  * Check a file descriptor for writability.
 441  *
 442  * \param fd The file descriptor.
 443  *
 444  * \return positive if fd is ready for writing, zero if it isn't, negative if
 445  * an error occurred.
 446  */
 447
 448 int write_ok(int fd)
 449 {
 450         struct timeval tv;
 451         fd_set wfds;
 452
 453         FD_ZERO(&wfds);
 454         FD_SET(fd, &wfds);
 455         tv.tv_sec = 0;
 456         tv.tv_usec = 0;
 457         return para_select(fd + 1, NULL, &wfds, &tv);
 458 }
 459
 460 /**
 461  * Ensure that file descriptors 0, 1, and 2 are valid.
 462  *
 463  * Common approach that opens /dev/null until it gets a file descriptor greater
 464  * than two.
 465  *
 466  * \sa okir's Black Hats Manual.
 467  */
 468 void valid_fd_012(void)
 469 {
 470         while (1) {
 471                 int fd = open("/dev/null", O_RDWR);
 472                 if (fd < 0)
 473                         exit(EXIT_FAILURE);
 474                 if (fd > 2) {
 475                         close(fd);
 476                         break;
 477                 }
 478         }
 479 }
 480
 481 /**
 482  * Traverse the given directory recursively.
 483  *
 484  * \param dirname The directory to traverse.
 485  * \param func The function to call for each entry.
 486  * \param private_data Pointer to an arbitrary data structure.
 487  *
 488  * For each regular file under \a dirname, the supplied function \a func is
 489  * called.  The full path of the regular file and the \a private_data pointer
 490  * are passed to \a func. Directories for which the calling process has no
 491  * permissions to change to are silently ignored.
 492  *
 493  * \return Standard.
 494  */
 495 int for_each_file_in_dir(const char *dirname,
 496                 int (*func)(const char *, void *), void *private_data)
 497 {
 498         DIR *dir;
 499         struct dirent *entry;
 500         int cwd_fd, ret2, ret = para_opendir(dirname, &dir, &cwd_fd);
 501
 502         if (ret < 0)
 503                 return ret == -ERRNO_TO_PARA_ERROR(EACCES)? 1 : ret;
 504         /* scan cwd recursively */
 505         while ((entry = readdir(dir))) {
 506                 mode_t m;
 507                 char *tmp;
 508                 struct stat s;
 509
 510                 if (!strcmp(entry->d_name, "."))
 511                         continue;
 512                 if (!strcmp(entry->d_name, ".."))
 513                         continue;
 514                 if (lstat(entry->d_name, &s) == -1)
 515                         continue;
 516                 m = s.st_mode;
 517                 if (!S_ISREG(m) && !S_ISDIR(m))
 518                         continue;
 519                 tmp = make_message("%s/%s", dirname, entry->d_name);
 520                 if (!S_ISDIR(m)) {
 521                         ret = func(tmp, private_data);
 522                         free(tmp);
 523                         if (ret < 0)
 524                                 goto out;
 525                         continue;
 526                 }
 527                 /* directory */
 528                 ret = for_each_file_in_dir(tmp, func, private_data);
 529                 free(tmp);
 530                 if (ret < 0)
 531                         goto out;
 532         }
 533         ret = 1;
 534 out:
 535         closedir(dir);
 536         ret2 = para_fchdir(cwd_fd);
 537         if (ret2 < 0 && ret >= 0)
 538                 ret = ret2;
 539         close(cwd_fd);
 540         return ret;
 541 }